From social isolation to sarcopenia: heterogeneous social isolation patterns and inflammatory mediation

Abstract Objectives The causal relationship between social isolation and sarcopenia remains unclear. This study investigated the association between social isolation and sarcopenia and explored the mediating role of systemic inflammation. Methods Data were derived from the 2011 and 2015 waves of the China Health and Retirement Longitudinal Study, comprising 7,059 community-dwelling participants aged over 45. Sarcopenia was defined according to the Asian Working Group for Sarcopenia 2019 criteria. Social isolation was measured using a four-item scale, incorporating marital status, household structure, frequency of contact with children, and social activity participation. Latent class analysis (LCA) identified distinct social isolation patterns. Logistic regression assessed the effect of social isolation on sarcopenia. Inverse probability weighting was used to control potential selection bias. Mediation analysis examined the role of systemic inflammation. Results During the 4-year follow-up, 490 participants developed sarcopenia. Socially isolated individuals had a significantly higher risk of sarcopenia (odds ratio [OR]: 1.34, 95% confidence interval [95% CI]: 1.01, 1.76) compared to their non-isolated peers. LCA identified three distinct social isolation patterns. Compared to the non-isolated groups, only individuals living alone and unmarried increased the risk of sarcopenia. Mediation analysis revealed systemic inflammation significantly mediated the association between social isolation and sarcopenia, accounting for 4.95% of the total effect. Discussion Social isolation increased the risk of sarcopenia among middle-aged and older Chinese adults, with systemic inflammation playing a partial mediating role. Among different social isolation patterns, those disconnected from their families have a higher risk of sarcopenia. Interventions strengthening family ties may help prevent or delay sarcopenia progression.